Breast pumps are devices which are designed to express milk from a mother's breast to a storage container, such as a feeding bottle to enable the mother to feed the breast milk to the baby at a later or more convenient time. Breast pumps generally comprise a funnel portion to receive the woman's breast, and a vacuum chamber coupled to each other, and a vacuum pump operable to repeatedly generate reduced pressure in the vacuum chamber, and thereby create a reduced pressure in the funnel, to stimulate the woman's breast to express milk into the funnel to be collected in the storage container connected to the vacuum chamber/funnel. In such breast pump devices, the vacuum pump can typically comprise a reciprocating piston or a reciprocating resilient membrane.
A breast pump device comprising a reciprocating resilient membrane for generating a vacuum is known from US 2001/038799, for example. US 2009/099511 discloses the use of a pump mechanism having a manually operable handle for effecting the vacuum. Both breast pump devices known from US 2001/038799 and US 2009/099511 include a mechanism to regulate vacuum within the funnel of the device, particularly minimum and maximum levels of the vacuum, wherein the mechanism comprises a valve-like construction for performing a sealing function in one position, and allowing air to escape in another position.
WO 2005/067997 also discloses the use of a pump mechanism having a handle for effecting the vacuum, wherein the handle is connected to a piston which is adapted to perform a reciprocating movement inside the breast pump device. In the funnel of the device, flexible membranes are arranged, which inflate during operation to massage the breast which is present inside the funnel.
Known breast pumps can include control means to enable the pressure depth generated by the vacuum pump within the vacuum chamber, and thereby at the breast funnel, to be regulated. Such known control means comprise varying the stroke of the reciprocating piston/resilient membrane, requiring the motor that drives the piston/resilient membrane and the transmission between the motor and the piston/resilient membrane to be able to operate in a reciprocating manner—namely to operate in two directions to enable the stroke of the reciprocating movement of the piston/resilient membrane to be varied. The construction of such a mechanism which includes a motor and transmission configured to operate in two directions in a reciprocating manner, as well as a motor control system to control such a configuration of mechanism, is complex and therefore results in a relatively high cost of manufacture. Furthermore, the reciprocating movement of the motor and transmission is not very energy efficient, leading to increased energy consumption, and such mechanisms can also lead to accelerated wear of the mechanical components. Yet further, motors which are capable of operating in two directions are more expensive than those which are capable of operating in only one single direction.
It would be advantageous to provide a pump apparatus suitable for use in a breast pump device which substantially alleviates or overcomes the problems mentioned above.